In general, characters written with a piece of chalk onto a blackboard are wiped away by a blackboard eraser and then the blackboard eraser having the chalk powder thereon is brushed off usually outside of a room window. At this time, chalk powder brushed off from the eraser is dispersed into the air and air in the room usually becomes polluted by the chalk powder. Breathing the polluted chalk powder containing air is bad for one's health.
Further, in order to overcome such problems, there have been provided a variety of devices for brushing the chalk powder from the eraser. However, most of the devices effect a removal of the chalk powder by rubbing the erasers having the powder thereon in the devices by hand.
One prior art device effects a removal of the chalk powder from the eraser by operating a brushing off rod having sharp protrusions and through holes up and down by an electric motor (Korean Utility Model Publication No. 1989-4786 publicated on Jul. 20, 1989). However, such a device has drawbacks due to the structure being complex and large in size, thereby occupying large spaces and are high in cost.